2008 GT, new exhaust, big mileage drop, help!

Tune it up.

You can get a Custom Tuned SCT X3 Programmer from Brenspeed for $379, tune problem solved for under $400. Also, save teh money on the MAF, return it if that is an option.

Ordered SCT sf3/x3 from AM at 379.00, including 3 custom tunes for my ride. Returning the JET MAF for $$$.
Already established contacts with Seattle Dyno shops for custom SCT Dyno tune in the near future.
I will provide feedback on performance once the tuner arrives.
I thank all of your for your input and guidance.
Once this is done I'll put up some new pics on my site and link ya.

Im pretty sure that mil eliminators dont work on the new stang. I may be wrong. My bullitt got 22-23 before i done the bbx o/r x and borlas then dropped to 15-16...after the sct custom tune, it went back to 22...try a tune because your car is running rich it sounds like.

You should have gone with a more reputable tuner like bamachips, vmp, or brenspeed. AM from what Ive read on here sells their tuners with canned tunes...correct me if im wrong...
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im getting pretty good mpg from my gt 500 after i put the jlt cai, and a tune from evo perf, if i recall im getting almost 24 mpg on the highway at 65 with cruise control, but not to good in town lucky if i get 14, maybe cuz the way i drive tho )

Got the tuner

Allright, got the tuner.

Tunes created:
87 econ
87 perf
91 perf

I have loaded the 87 econ tune and I have tried the 87 perf tune and now my engine light is back off, no dtc codes listed. Exhaust still smells rich with either tune, though the engine does sound smoother. No noticeable increase in mileage. I'm not impressed

I am going to put some more miles on and give it the rest of my tank, got about 1/3rd left. Then I'm going to load 91 and see what's up. But my first experience is not exciting.

stay tuned for the next episode of, got stang, now what?

They sell different options. No tune is truly custom unless it's created for you on the dyno. That said, I looked at a few companies and went with SCT. They offer a few different options aned have dyno shops within range that can create me really cusom tunes I can use on my device.

As far as AM and the tuners go. You can buy a preloaded tuner, or you can buy a tuner and they will create you custom tunes, based on what you have for mods, load them on the unit and send it to you.

I chose 3 different octanes that I wanted and filled out their webform listing all my mods, 3 days later I have the flash device which loads the tuner.

I can also tweak each tune myself to some degree.

I got mine through AM which is nice, because whenever I order something from them I get tune files for the new mod emailed to me free.

Without cats the exhaust will smell different. AM tunes are not as good as a Bamachips or Brenspeed tune...not sure why you didnt do your research before you started all this the search box is your friend....I have a Bamachips tune which leaned my car too much so I called and had a slightly richer tune sent....pretty easy. Fuel economy is the same and performance is greatly improved...I bought from Bamachips based on his rep as being a great tuner and very helpful after the sale...search box was my friend. You can have him email u a custom tune for 50 bucks since you didnt buy it from him....it will solve your problem unless the problem is more involved....

I'm kinda concerned the basic caned tune may not 100% fix your issue. My understanding of the workings of fuel injection is this (and I could be wrong).

There a two basic modes the system operates in after it's warmed up. Full throttle mode that meters the MAF, uses pre-programed A/F tables and ignores the O2 sensors. Then there's non full throttle that monitors all sensors and attempts to keep the optimal A/F and give the best drive-ablity and fuel economy. When we tune our cars typically we tune to adjust the A/F in the tables for wide open throttle where the O2s are not trying to correct this. Your issue is the relocation of the O2s further down stream has your computer freaked out in non full throttle mode.

I've seen 5.0s with bad 02 sensors that got bad gas mileage, surged, and generally ran like crap under normal conditions, but under full throttle they ran great. I bet some others have had similar experiences with cars that ran great at WOT, but like crap otherwise. My suggestion is to call Bamachips and just ask them what they think can be done.

I think it's to early to make major judgments, I just didn't see a night and day difference and people tend to claim and I had hoped to experience.

I mentioned above that I needed to do more driving and that I have not yet used the 91 Octane tune. I understand that is really where you see the performance difference according to forums and tech documentation.

I also stated above that these are not canned pre-programmed tunes.
These are tunes based on the build of your vehicle. Most SCT tuners use similar software to make the tunes, but the shops may have philosophical differences of what they tweak. Some individual tune techs may know their stuff better than others, sure.

Lastely, I actually have done alot of reseach before buying this tuner, even before my problem I was looking into tuners down the road. Let's not forget at the start of the thread I metnioned cost was an issue. I also mentioned during the thread I plan to have add a true dyno tune soon.
That said, from what I can tell on the net people overall are happy with all of their tuners and tunes, regardless of make and tech. I have yet to find more than one or two complaint anywhere about most of these products, so I feel you can't really go wrong with any of then, though you may be able to do better.

I finally did some actual distance and mixed driving and mileage numbers are above pre-tuner averages with the new 87 economy tune. So that's good, no check engine light, no codes, everything seems to be within parameters from what I can tell. The exhaust/engine also feels smoother. The smell is still pretty pungent, yes. But I can play with the AF and WOT a little bit and see what happens.

Any good threads about that? I'm not finding any searching this forum.

I am really looking forward to trying the 91 octane performance tune. I should be able to tell a night and day difference, I'll keep my fingers crossed.

Thank you all for the input. Yes, I can get a tune from anybody now that I have the tuner. Some people charge 50 bucks, some 25, but they are out there as you have mentioned Brenspeed, and others. AM will also give me more tunes f I am not satisfied as well, so I can try that. I am hoping these will do until I can get a dyno tune which runs about 500 bucks.

My biggest issue now is the smell and determining if it is a problem or not. That will have to wait now that all the money for this season is gone.
At this point, I'm going to say f'it and drive it.

Thanks Dan, I will drive it and trying the different tunes for a couple weeks and then call the other vendors for their thoughts if I'm still not satisfied. I see your point, I find those explanations really useful as I am still learing all of this computer crap. Man I miss carbs sometimes.

One guy mentioned that w/o cats things will be smelly anyway, maybe I just need to get used that that part.

Darkfire, you mention your mileage is great on the 93 tune. We only have 91, hence the 91 tune. But I live in MT, I can drive 80 all the time, so I doubt I'll see that mileage with any tune. I can't drive 55 bro, specially with a perf tune. I will do my best and try different styles and see what I can erk out of my machine. The way I see it though, 20mpg is good enough if I'm having fun.


I have a road trip to Seattle in September which will be a great test. I have already done that drive several times with the vehicle before the current mods so it will be interesting.

Thanks again guys.

Raven6, I haven't had cats on a car in 10 years and yes not having cats is going to make your exhaust smell somewhat rich. However, you can tell a difference from a car that is running the correct A/F and one that's running extremely rich by smelling the exhaust. It should smell with no cats but not like it's dumping raw fuel in the exhaust.

Thanks Dan, I would agree with you, but I don't think I am qualified enough to tell by smell. It's better now that I am running the 91 and 91 perf tune.
The car is better all the way around on the 91 with the perf tune and I am averaging about 20 which is still acceptable. I plan on doing a long highway roadtrip in sept and I will be able to stay at high speeds and see what the mileage is like. I am suspecting I will see about 22-23 mpg on that ride. Which is what I was getting before upgrades. So, more power, no loss of economy, I'm content.

Thank you, also, enjoyed the comments on Lambo doors on this site. :OT:Hilarious. My friend keeps harassing me to do that mod, and now I have some cool come back lines